Finding Help From Within the Shell

Note: Please look further down about help facilities specific to SDF, like the FAQ!

While the UNIX shell may seem a bit daunting and cold with cryptic two-letter commands, dozens of command line switches, and no animated paper clips to show you the way, there are several different ways of getting help from the system.

The easiest and most comprehensive way of getting help is reading the manpage. You've probably heard RTFM (Read The Fscking Manual) somewhere throughout your computer use, well, this is that Manual. Manpages are the standard form of documentation for every UNIX. Learn to use them. Learn to love them.

Where can you find them? It's pretty simple. Think of a command. (ls, rm, chmod, kill, grep) or a program (vi, mutt, snarf, majordomo) So go ahead, type

• man command

command being the name of the command you want to learn about. As you can see, manpages are broken down into sections. We'll use mkdir as an example.

man mkdir

  MKDIR(1)                NetBSD General Commands Manual
  MKDIR(1)

  NAME
       mkdir - make directories

  SYNOPSIS
       mkdir [-p] [-m mode] directory_name ...

  DESCRIPTION
       mkdir creates the directories named as operands, in the order specified,
       using mode rwxrwxrwx (0777) as modified by the current umask(2).

       The options are as follows:

       -m      Set the file permission bits of the final created directory to
               the specified mode.  The mode argument can be in any of the for-
               mats specified to the chmod(1) utility.  If a symbolic mode is
               specified, the operation characters ``+'' and ``-'' are inter-
               preted relative to an initial mode of ``a=rwx''.

       -p      Create intermediate directories as required.  If this option is
               not specified, the full path prefix of each operand must already
               exist.  Intermediate directories are created with permission bits
               of rwxrwxrwx (0777) as modified by the current umask, plus write
               and search permission for the owner.  Do not consider it an error
               if the argument directory already exists.

       The user must have write permission in the parent directory.

  EXIT STATUS
       mkdir exits 0 if successful, and >0 if an error occurred.

  SEE ALSO
       chmod(1), rmdir(1), mkdir(2), umask(2)

  STANDARDS
       The mkdir utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compat-
       ible.

  NetBSD 2.0.2                   January 25, 1994                   NetBSD
  2.0.2

For our “mkdir” command, the man page displayed has six sections: NAME, SYNOPSIS, DESCRIPTION, EXIT STATUS, SEE ALSO, and STANDARDS. The NAME section simply shows the name of the command and a terse description of its function. The SYNOPSIS gives a brief outline of the command syntax, so you can see what the command you enter should look like. Items in square brackets [ ] are optional. The DESCRIPTION section provides a detailed description of how the command works, including information on the various options or modes of the command. The EXIT STATUS section describes what status codes are generated by the command when it completes (successfully or unsuccessfully). These codes can be read by programs (such as a shell script) to determine how to react to the command's result. SEE ALSO provides cross referencing information for related commands or others which may be helpful. And finally, the STANDARDS section lists information on which standards this particular command complies with.

The manual is divided up into nine sections:

1. User commands.
2. System calls and error numbers.
3. Functions in the C libraries.
4. Device drivers.
5. File formats.
6. Games and other diversions.
7. Miscellaneous information.
8. System maintenance and operation commands.
9. Kernal developers.

In some cases, the same topic will appear on more than one section of the manual. For example, there is a chmod user command and a chmod() system call. How would you find the appropriate manpage? You can tell man which section you'd like to look under. If you wanted to find the user command you would type:

• man 1 chmod

This would display the manpage for the user command chmod. References to the specific sections are traditionally placed in parenthesis after the command name like so: chmod(1)

Well, this is all fine and good if you know the name of the command, but what if you can't remember the name? 'man -k' can be used to search for keywords in the command descriptions. So, if you want to find a mail program you would type:

• man -k editor

A list of commands with the keyword “editor” in their descriptions will be presented on the screen.

For programs of the GNU Project, you may also use the “info” command. If you know the name of a program, give it as an argument (like with “man”).
In fact, you can use “info” as an alias to “man”, because the info reader will simply display the man page if it cannot find an info entry (but you cannot specify the manpage section).

However, navigation is different in the standard info reader, as it is based on the “emacs” text editor.
Quick key help (for more, consult “info info”):

With most terminals, you can also move around using the cursor keys (arrows).

There are also a number of tools at SDF that you can use to get more help. Type the following commands at a shell prompt.

The SDF help system.

A collection of frequently asked questions. Type 'g ' to enter a topic, 'l' to list the questions in the topic, and 't ' to read the FAQ. The FAQ is also available on the SDF website.

If you cannot find your answer in the man pages, help, faq, or googling post a question to the helpdesk and a friendly member of the community will answer your question. Any member with ARPA status can login as an attendent to answer questions. Please note: in helpdesk you should only post questions directly related to SDF's systems, but not about general UNIX, programming or gardening - these belong to the bboard!

Com and bboard are meeting places for the SDF community. You could also pose your question there. Bboard and faq have the same interface. See COM is not IRC for how to use com.

And of course there are the online tutorials that you are reading right now! The top level page is tutorials.

$Id: findinghelp.html,v 1.10 2007/04/20 07:36:18 yargo Exp $